He said that while no bilateral talks were planned with the Ukrainian president, such a meeting could not be ruled out.

In a brief news conference after the talks, Italian Prime Minister Renzi said they were constructive but big differences remained.

"I think we made a step ahead," he said.

I would underline the real desire to find a solution and we can be positive."

Meanwhile the UK prime minister said Putin had made it clear he did not want a frozen conflict or a divided Ukraine.

But David Cameron added that the sanctions would be kept in place until actions agreed as part of a peace plan last month in the Belarusian capital Minsk were taken.

The BBC's Damian Grammaticas in Milan says the talks were an unusual opportunity for the sides to get talking and build some sort of trust, which has so far been severely lacking.

Minsk memorandum: Key points

To pull heavy weaponry 15km (nine miles) by each side from the line of contact, creating a 30km security zone

To ban offensive operations

To ban flights by combat aircraft over the security zone

To set up an OSCE monitoring mission

To withdraw all foreign mercenaries from the conflict zone

President Poroshenko met Ms Merkel ahead of Friday's talks, with both expressing regret that many points of the peace plan "had not yet been implemented", German government sources were quoted as saying by the AFP news agency.

Ms Merkel also met Putin for two-and-a-half hours late at night on Thursday after the Russian president arrived late for the summit.

Among other points, the plan envisages the withdrawal of heavy weaponry 15km (10 miles) by each side from the line of contact and the withdrawal of all foreign "mercenaries" from the conflict zone.